ECU - Electronic Control Unit Connector.
The 1999–2000 Honda Civic Engine Control Module (ECM/PCM) is an OBD2 unit fitted to the EK-chassis Civic (EK4/EK8/EJ8) and manages the PGM-FI multi-point fuel injection system. It interfaces with the vehicle via three multi-pin connectors labelled A, B, and C, and communicates with diagnostic equipment through the 16-pin Data Link Connector (DLC) per SAE J1962. Compared with the 1996–98 Civic ECM, the 1999–2000 variant relocates the VTEC solenoid valve signal to pin B12 (from A8) and the VTEC oil-pressure switch to pin C10 (from C15). The ECM is located above the passenger-side footwell.
Connector A
| Pin | name | Signal |
|---|---|---|
| A19 | Engine Speed Pulse | RPM |
| A23 | Secondary O2 Sensor | Analog |
| A32 | Brake Switch | Analog |
Connector B
| Pin | name | Signal |
|---|---|---|
| B10 | Power Ground | Ground |
| B12 | VTEC Solenoid Valve | Analog |
Connector C
| Pin | name | Signal |
|---|---|---|
| C10 | VTEC Pressure Switch | Analog |
| C16 | Primary O2 Sensor | Analog |
| C17 | MAP Sensor | Analog 0.32V @ -13.9 PSI 4.84V @ 10.94 PSI |
| C23 | Vehicle Speed Sensor | Speed |
| C25 | Intake Air Temperature Sensor | Analog |
| C26 | Engine Coolant Temperature Sensor | Analog |
| C27 | Throttle Position Sensor | Analog |
Notes
- All connector pins are read from the wire side (rear of connector), not the pin face, with the locking tab at the top; this orientation determines the correct pin numbering.
- The ECM/PCM Reset Procedure is documented in the factory service manual: disconnect the negative battery terminal for at least 30 seconds, or remove the ECM backup fuse. Resetting clears stored DTCs and idle-learn data; an idle relearn procedure is required afterwards.
- VTEC-equipped engines (B16A2) use pin B12 for the solenoid valve output and C10 for the oil-pressure switch input. Non-VTEC models (D16Y7) do not use these pins.
- The 16-pin DLC (Data Link Connector) is located under the dashboard and accepts standard OBD2 scan tools per SAE J1962.
Signals
- A19 (Engine Speed Pulse) — RPM signal derived from the crankshaft/distributor; used by the ECM to calculate engine speed for fuelling and ignition timing.
- A23 (Secondary O2 Sensor) — Analogue input from the downstream (post-catalytic converter) heated oxygen sensor; used for catalyst efficiency monitoring.
- A32 (Brake Switch) — Digital input indicating brake pedal application; used by the ECM for torque converter lock-up and idle control.
- B10 (Power Ground) — ECM chassis ground reference.
- B12 (VTEC Solenoid Valve) — ECM output that energises the VTEC oil-control solenoid to switch cam profiles on VTEC-equipped engines (1999–2000 position; 1996–98 Civic used A8).
- C10 (VTEC Pressure Switch) — Input confirming VTEC oil pressure has risen sufficiently after solenoid activation (1999–2000 position; 1996–98 Civic used C15).
- C16 (Primary O2 Sensor) — Analogue input from the upstream (pre-catalytic converter) heated oxygen sensor; used for closed-loop fuelling correction.
- C17 (MAP Sensor) — Analogue manifold absolute pressure input; 0.32 V at −13.9 PSI vacuum, 4.84 V at +10.94 PSI boost; used for load calculation.
- C23 (Vehicle Speed Sensor) — Pulse signal from the vehicle speed sensor (VSS); used for speed-dependent fuelling, idle control, and instrument cluster drive.
- C25 (Intake Air Temperature Sensor) — Analogue input (NTC thermistor) measuring inlet air temperature for fuel charge density correction.
- C26 (Engine Coolant Temperature Sensor) — Analogue input (NTC thermistor) measuring coolant temperature for warm-up enrichment and cooling fan control.
- C27 (Throttle Position Sensor) — Analogue voltage input proportional to throttle plate angle; used for acceleration enrichment and idle detection.